1. Field of the Invention
This invention generally relates to integrated circuit (IC) fabrication and, more particularly, to an inductor with transverse interfaces to minimize parasitics and size.
2. Description of the Related Art
Conventional digital systems fabricated on a single printed circuit board (PCB) or a collection of connected PCBs still often require analog circuitry. For example, analog circuits are often used in active buffers to boost a signal between communication nodes, or as an oscillator to create a reference signal. In both applications, inductors are used to peak or tune the signal to a desired frequency. The problem is that inductors tend to be large bulky components, and the electrical performance of bigger inductors (with higher quality (Q) factors and lower loss) is generally more desirable. The use of large inductors on PCBs results in higher costs, greater assembly complications, and a larger overall package size.
FIG. 1 is a schematic of a differential signal inductor-capacitor (LC) delay line (prior art). LC delay lines are often a component in analog circuits. Since large value capacitors are also bulky components, LC delay lines are especially problematic in IC fabrication. The delay line 100 is made by series connecting a plurality of inductors, and connecting the center tap of each inductor to a capacitor 104. Long interconnects between inductors are undesirable, as they create parasitics. The parasitics degrade loss and group delay, and make the circuit frequency dependent.
FIG. 2 is a plan of an inductor with a center tap, suitable for IC applications (prior art). The dotted lines represent a bridge between line segments that is enabled through vias to an adjacent circuit layer. The interconnects (input/output) 202 to the inductor 200 contribute to the overall space on an IC level that must be devoted to an inductor. Also shown is a center tap (tap) 204 from the center of the inductor, at a line length equally distanced from the input and output.
It would be advantageous if a PCB-style inductor could be designed especially for use in analog circuits that require low parasitics and a small size.